TODAY’S STUDY: WHERE GEOTHERMAL IS HEADED

Question: What two things do makers of solar system inverters, renewable energy researchers in the UK and drillers for geothermal energy in the Pacific Ocean’s Ring of Fire have in common?

Answer: (1) They were all featured in lead studies this week at NewEnergyNews and (2) each lead study reported that the key to achieving full potential is supportive policy.

Enough supportive policy could, presumably, also turn Amy Winehouse into Oprah Winfrey. (Well…) The point: Why bother mentioning it? Just like oil and coal, solar hardware and UK renewable energy and geothermal production will have to make it in the marketplace with whatever support they can get, right?

Yes, exactly. Just like oil and coal. Those energy sources came along at times in history when they were vital to economic dominance and where they thrived it was due to enormous support.

Supportive policy did not mean the same thing in 18th century England and the 19th century U.S. as it does now. In both places, the government got the railroad crucial to coal’s transport built and let the coal bosses take care of the rest. The result: Black rocks fueled the industrial revolution.

In the wake of World War II, the U.S. oil industry – which had fueled the Allied victory – realized the future of oil production was in the Middle East. But the industry also realized it couldn’t produce and deliver cheap oil while both paying royalties there and taxes here. It's lobbyists went to work and soon Congress gave the industry a tax break so gratuitous it was nicknamed “the golden gimmick.” The result: Oil mostly replaced coal as the heating fuel of choice by the 1970s and the nation got lots of kicks on Route 66.

Nothing has changed except that the world now needs a new kind of energy.

Bullies control the oil, coal dependent economies from Greece to Illinois are crumbling, unemployment in U.S. cities is approaching Great Depression levels, lung disease is epidemic and scientists just announced that climate change has put the world’s ocean life at the brink of mass extinctions.

Just like they always have, governments must provide policy support for a transition. Policies must support both developed and emerging economies in getting their cars on the grid and cleaning up their grids through a shift to whatever each nation has of this good earth’s sun, wind, deep heat and flowing waters.

As the study highlighted below reports, untapped geothermal resources await discovery and the opportunity to play a key role in the transition to a New Energy economy that will free the world’s nations from oil dependence, rejuvenate their domestic economies, put their people back to work, ease over-burdened health care systems and restore an ecosystem at the edge of catastrophe.

Supportive policy is what governments always have and always should provide. All political leaders need do is take an unlobbied look at today’s options and the logic of New Energy will be undeniable.

Technology Roadmap; Geothermal Heat and Power
June 2011 (International Energy Agency)

Key findings

Geothermal energy can provide low-carbon base-load power and heat from high-temperature hydrothermal resources, deep aquifer systems with low and medium temperatures, and hot rock resources. This roadmap envisages development and deployment of geothermal heat and power along the following paths:

zz By 2050, geothermal electricity generation could reach 1 400 TWh per year, i.e. around 3.5% of global electricity production, avoiding almost 800 megatonnes (Mt) of CO2 emissions per year.

zz Geothermal heat could contribute 5.8 EJ (1 600 TWh thermal energy) annually by 2050, i.e. 3.9% of projected final energy for heat.

zz In the period to 2030, rapid expansion of geothermal electricity and heat production will be dominated by accelerated deployment of conventional high-temperature hydrothermal resources, driven by relatively attractive economics but limited to areas where such resources are available. Deployment of low- and medium-temperature hydrothermal resources in deep aquifers will also grow quickly, reflecting wider availability and increasing interest in their use for both heat and power.

zz By 2050, more than half of the projected increase comes from exploitation of ubiquitously available hot rock resources, mainly via enhanced geothermal systems (EGS)…Substantially higher research, development and demonstration (RD&D) resources are needed in the next decades to ensure EGS becomes commercially viable by 2030.

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zz A holistic policy framework is needed that addresses technical barriers relating to resource assessment, accessing and engineering the resource, geothermal heat use and advanced geothermal technologies. Moreover, such a holistic framework needs to address barriers relating to economics, regulations, market facilitation and RD&D support.

zz Policy makers, local authorities and utilities need to be more aware of the full range of geothermal resources available and of their possible applications. This is particularly true for geothermal heat, which can be used at varying temperatures for a wide variety of tasks.

zz Important R&D priorities for geothermal energy consist of accelerating resource assessment, development of more competitive drilling technology and improving EGS technology as well as managing health, safety and environmental (HSE) concerns.

zz Advanced technologies for offshore, geopressured and super-critical (or even magma) resources could unlock a huge additional resource base. Where reasonable, co-produced hot water from oil and gas wells can be turned into an economic asset.

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Key actions in the next 10 years

zz Establish medium-term targets for mature and nearly mature technologies and long- term targets for advanced technologies, thereby increasing investor confidence and accelerating expansion of geothermal heat and power.

zz Introduce differentiated economic incentive schemes for both geothermal heat (which has received less attention to date) and geothermal power, with incentives phasing out as technologies reach full competitiveness.

zz Develop publicly available databases, protocols and tools for geothermal resource assessment and ongoing reservoir management to help spread expertise and accelerate development.

zz Introduce streamlined and time-effective procedures for issuing permits for geothermal development.

zz Provide sustained and substantially higher research, development and demonstration (RD&D) resources to plan and develop at least 50 more EGS pilot plants during the next 10 years.

zz Expand and disseminate the knowledge of EGS technology to enhance production, resource sustainability and the management of health, safety and environmental (HSE) performance.

zz In developing countries, expand the efforts of multilateral and bilateral aid organisations to develop rapidly the most attractive available hydrothermal resources, by addressing economic and non-economic barriers.

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Introduction

There is a pressing need to accelerate the development of advanced energy technologies in order to address the global challenges of providing clean energy, mitigating climate change and sustainable development. This challenge was acknowledged by the ministers from G8 countries, China, India and South Korea, in their meeting in June 2008 in Aomori, Japan, where they declared the wish to have the IEA prepare roadmaps to advance innovative energy technology.

“We will establish an international initiative with the support of the IEA to develop roadmaps for innovative technologies and co-operate upon existing and new partnerships, including carbon capture and storage (CCS) and advanced energy technologies. Reaffirming our Heiligendamm commitment to urgently develop, deploy and foster clean energy technologies, we recognize and encourage a wide range of policy instruments such as transparent regulatory frameworks, economic and fiscal incentives, and public/private partnerships to foster private sector investments in new technologies…”

To achieve this ambitious goal, the IEA has undertaken an effort to develop a series of global technology roadmaps covering the most important technologies. These technologies are evenly divided among demand-side and supply-side technologies. This geothermal energy roadmap is one of the roadmaps being developed by the IEA.

The overall aim of these roadmaps is to demonstrate the critical role of energy technologies in achieving the stated goal of halving energy-related carbon dioxide (CO2) emissions by 2050. The roadmaps will enable governments, industry and financial partners to identify the practical steps they can take to participate fully in the collective effort required.

This process began with establishing a clear definition and the elements needed for each roadmap. Accordingly, the IEA has defined its global technology roadmaps as:

“… a dynamic set of technical, policy, legal, financial, market and organizational requirements identified by the stakeholders involved in its development. The effort shall lead to improved and enhanced sharing and collaboration of all related technology-specific research, development, demonstration and deployment (RDD&D) information among participants. The goal is to accelerate the overall RDD&D process in order
to enable earlier commercial adoption of the technology in question.”

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Rationale for geothermal energy

Geothermal technologies use renewable energy resources to generate electricity and/or heating and cooling while producing very low levels of greenhouse-gas (GHG) emissions (Box 1). They thus have an important role to play in realizing targets in energy security, economic development and mitigating climate change.

Geothermal energy is stored in rock and in trapped vapour or liquids, such as water or brines; these geothermal resources can be used for generating electricity and for providing heat (and cooling). Electricity generation usually requires geothermal resources temperatures of over 100oC. For heating, geothermal resources spanning a wider range of temperatures can be used in applications such as space and district heating, spa and swimming pool heating, greenhouse and soil heating, aquaculture pond heating, industrial process heating and snow melting. Space cooling can also be supplied through geothermal heat, through the use of heat-driven adsorption chillers as an alternative to electrically driven compression chillers.

Even the modest temperatures found at shallower depths can be used to extract or store heat for heating and cooling by means of ground source heat pumps (GSHP, Box 2). GSHP are a widespread application for geothermal energy, especially in colder climates, but they follow a different concept from deep geothermal heat technologies and address a different market, so for reasons of clarity this roadmap excludes them.

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Global technical potential for geothermal electricity has been estimated at 45 EJ/yr — 12 500 TWhe, i.e. about 62% of 2008 global electricity generation (Krewitt et al. 2009). The same study estimated resources suitable for direct use at 1 040 EJ/yr — 289 000 TWht; worldwide final energy use for heat in 2008 was 159.8 EJ/44 392 TWht (Ibid.). The estimated technical potential for geothermal electricity and geothermal heat excludes advanced geothermal technologies that could exploit hot rock or off-shore hydrothermal, magma and geopressured resources. Although geothermal energy has great technical potential, its exploitation is hampered by costs and distances of resource from energy demand centres.

Geothermal typically provides base-load generation, since it is generally immune from weather effects and does not show seasonal variation…Capacity factors of new geothermal power plants can reach 95%. The base-load characteristic of geothermal power distinguishes it from several other renewable technologies that produce variable power. Increased deployment of geothermal energy does not impose load balancing requirements on the electricity system. Geothermal power could be used for meeting peak demand through the use of submersible pumps tuned to reduce fluid extraction when demand falls. However, procedures and methods that allow for a truly load-following system have yet to be developed. Geothermal energy is compatible with both centralised and distributed energy generation and can produce both electricity and heat in combined heat and power (CHP) plants.

Geothermal technology development has focused so far on extracting naturally heated steam or hot water from natural hydrothermal reservoirs. However, geothermal energy has the potential to make a more significant contribution on a global scale through the development of the advanced technologies, especially the exploiting of hot rock resources4 using enhanced geothermal systems (EGS) techniques that would enable energy recovery from a much larger fraction of the accessible thermal energy in the Earth’s crust. In the IEA geothermal roadmap vision, geothermal energy is projected to provide 1 400 TWh annually for global electricity consumption in 2050, following the IEA Energy Technology Perspectives 2010 Blue Hi-REN scenario. Geothermal heat use is projected to supply 5.8 EJ/yr in 2050.

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Geothermal energy today

Development of geothermal energy

Although the use of geothermal hot springs has been known since ancient times, active geothermal exploration for industrial purposes started at the beginning of the 19th century with the use of geothermal fluids (boric acid) in Larderello (Italy). At the end of the 19th century, the first geothermal district heating system began operating in Boise (United States), with Iceland following in the 1920s. At the start of the 20th century, again in Larderello, the first successful attempt to produce electricity from geothermal heat was achieved. Since then, installed geothermal electricity has steadily increased.

In 2009, global geothermal power capacity was 10.7 GWe and generated approximately 67.2 TWhe/ yr of electricity, at an average efficiency rate of 6.3 GWh/MWe (Bertani, 2010) (Figure 1). A remarkable growth rate from 1980 to 1985 was largely driven by the temporary interest of the hydrocarbon industry – mainly Unocal (now merged with Chevron) – in geothermal energy, demonstrating the considerable influence on the geothermal market of attention from the hydrocarbon sector, which has expertise similar to that needed for geothermal development. Geothermal electricity provides a significant share of total electricity demand in Iceland (25%), El Salvador (22%), Kenya and the Philippines

Geothermal electricity provides a significant share of total electricity demand in Iceland (25%), El Salvador (22%), Kenya and the Philippines (17% each), and Costa Rica (13%). In absolute figures, the United States produced the most geothermal electricity in 2009: 16 603 GWhe/ yr from an installed capacity of 3 093 MWe. Total installed capacity of geothermal heat (excluding heat pumps) equalled 15 347 MWt in 2009, with a yearly heat production of 223 petajoules (PJ); China shows the highest use of geothermal heat (excluding heat pumps), totalling 46.3 PJ/yr geothermal heat use in 2009 (Lund et al., 2010).

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Geothermal resources

Hydrothermal resources

Until recently, utilisation of geothermal energy was concentrated in areas where geological conditions permit a high-temperature circulating fluid to transfer heat from within the Earth to the surface through wells that discharge without any artificial lift. The fluid in convective hydrothermal resources can be vapour (steam), or water-dominated, with temperatures ranging from 100oC to over 300oC. High-temperature geothermal fields are most common near tectonic plate boundaries, and are often associated with volcanoes and seismic activity, as the crust is highly fractured and thus permeable to fluids, resulting in heat sources being readily accessible (Figure 2).

Most plate boundaries are below sea level. There are 67 000 km of mid-ocean ridges, of which 13 000 km have been studied, and more than 280 sites with submarine geothermal vents have been discovered (Hiriart et al., 2010). Some submarine vents have been estimated to be able to realise capacities ranging from 60 MWt to 5 GWt (German et al., 1996). In theory, such geothermal vents could be exploited directly without drilling and produce power by means of an encapsulated submarine binary plant. However, R&D is needed since there are no technologies available to commercially tap energy from off-shore geothermal resources.

Geothermal heat can also be economically extracted from many deep aquifer systems all over the world. Many such locations can be reached within a depth of 3 km, with moderate heat flow in excess of 50 MW/m2 to 60 MW/m2 and rock and fluid temperatures of in excess of 60oC (Figure 3).

The actual local performance depends strongly on the natural flow conditions of the geothermal reservoir. Geo-pressured deep aquifer systems contain fluids at pressures higher than hydrostatic.

Water co-produced during oil and gas exploitation is another type of hydrothermal resource. Oil and gas wells can produce warm water that is often seen by operators as a by-product with limited commercial upside. Examples are known of aging oil fields in North America that can produce up to 100 million liters of geothermally heated water per day. This could be turned into an asset by extracting the energy contained in the produced water by means of binary cycle power plants.

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Hot rock resources

So far, utilisation of geothermal energy has been concentrated in areas of naturally occurring water or steam, and sufficient rock permeability. However, the vast majority of geothermal energy within drilling reach – which can be up to 5 km, given current technology and economics – is in relatively dry and low-permeability rock. Heat stored in low-porosity and/or low-permeability rocks is commonly referred to as hot rock resources. These resources are characterized by limited pore space and/or minor fractures and therefore contain insufficient water and permeability for natural exploitation.

Hot rock resources can be found anywhere in the world, although they are found closer to the surface in regions with an increased presence of naturally occurring radioactive isotopes (e.g. South Australia) or where tectonics have resulted in a favorable state of stress (e.g. in the western USA). In stable, old continental tectonic provinces, where temperature gradients are low (7°C/km to 15°C/km) and permeability is low but with less favorable state of stress, depths will be significantly greater and developing an EGS resource will be less economic.

Technologies that allow energy to be tapped from hot rock resources are still in the demonstration stage and require innovation and experience to become commercially viable. The best-known such technology is enhanced geothermal systems (EGS;6 Box 3). Other approaches to engineering hot rock resources, which are still at the conceptual phase, try methods other than fracturing the hot rock. Such technologies aim instead to create connectivity between water inlet and water outlet, for example by drilling a sub-surface heat exchanger made of underground tubes or by drilling a 7 km to 10 km vertical well of large diameter that contains water inlet and water outlet at different depths.

A global map of hot rock resources is not yet available, but some countries have started mapping EGS resources, including the United States (Figure 5).

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Current technologies

Electricity production

Most conventional power plants use steam to generate electricity. Whereas fossil-fuel plants burn coal, oil or gas to boil water, many existing geothermal power plants use steam produced by “flashing” (i.e. reducing the pressure of) the geothermal fluid produced from the reservoir. Geothermal power plants today can use water in the vapour phase, a combination of vapour and liquid phases, or liquid phase only. The choice of plant depends on the depth of the reservoir, and the temperature, pressure and nature of the entire geothermal resource. The three main types of plant are flash steam, dry steam and binary plants. All forms of current accepted geothermal development use re-injection as a means of sustainable resource exploitation.

Flash steam plants

The most commonly found geothermal resources contain reservoir fluids with a mixture of hot liquid (water) and vapour (mostly steam). Flash steam plants, making up about two-thirds of geothermal installed capacity today, are used where water dominated reservoirs have temperatures above 180°C. In these high-temperature reservoirs, the liquid water component boils, or “flashes,” as pressure drops. Separated steam is piped to a turbine to generate electricity and the remaining hot water may be flashed again twice (double flash plant) or three times (triple flash) at progressively lower pressures and temperatures, to obtain more steam. The cooled brine and the condensate are usually sent back down into the reservoir through injection wells. Combined-cycle flash steam plants use the heat from the separated geothermal brine in binary plants to produce additional power before re-injection.

Dry steam plants

Dry steam plants, which make up about a quarter of geothermal capacity today, directly utilise dry steam that is piped from production wells to the plant and then to the turbine. Control of steam flow to meet electricity demand fluctuations is easier than in flash steam plants, where continuous up-flow in the wells is required to avoid gravity collapse of the liquid phase. In dry steam plants, the condensate is usually re-injected into the reservoir or used for cooling.

Binary plants

Electrical power generation units using binary cycles constitute the fastest-growing group of geothermal plants, as they are able to use low- to medium-temperature resources, which are more prevalent. Binary plants, using an organic Rankine cycle (ORC) or a Kalina cycle, typically operate with temperatures varying from as low as 73oC (at Chena Hot Springs, Alaska) to 180°C. In these plants, heat is recovered from the geothermal fluid using heat exchangers to vaporise an organic fluid with a low boiling point (e.g. butane or pentane in the ORC cycle and an ammonia-water mixture in the Kalina cycle), and drive a turbine. Although both cycles were developed in the mid-20th century, the ORC cycle has been the dominant technology used for low-temperature resources. The Kalina cycle can, under certain design conditions, operate at higher cycle efficiency than conventional ORC plants. The lower-temperature geothermal brine leaving the heat exchanger is re-injected back into the reservoir in a closed loop, thus promoting sustainable resource exploitation. Today, binary plants have an 11% share of the installed global generating capacity and a 44% share in terms of the number of plants (Bertani, 2010).

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Geothermal heat use

Heat demand represents a significant share of final energy consumption in cooler regions such as northern Europe, northern USA, Canada and northern China. In warmer climates, heat demand is dominated by industrial process heat, but may still account for a considerable share of energy consumption. Geothermal heat use can cover several types of demand at different temperature levels. Even geothermal resources at temperatures of 20oC to 30oC (e.g. flood water in abandoned mines) may be useful to meet space heating demand.

The most widely spread geothermal heat use application, after ground source heat pumps (49% of total geothermal heat), is for spa and swimming pool heating (about 25%), for instance in China, where it makes up 23.9 PJ out of the 46.3 PJ of geothermal heat used annually (excluding ground source heat pumps). The next-largest geothermal heat usage is for district heating (about 12%), while all other applications combined make up less than 15% of the total. The potential for considerable growth in the use of geothermal energy to feed district heating networks should be exploited, both in large, newly built environments and as a replacement for existing fossil-fuelled district heating systems.

Geothermal “heat only” plants can feed a district heating system, as can the hot water remaining from electricity generation, which can also be used in a cascade of applications demanding successively lower temperatures. These might start with a district heating system, followed by greenhouse heating and then perhaps an aquaculture application.

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At the time of the oil price peak in 2008, for example, Dutch horticultural entrepreneurs demonstrated that geothermal heat at 60oC could cover 60% to 90% of the energy demand for tomato-growing (Van Dijk, 2009). The 2008 oil and gas prices resulted in strong interest in geothermal projects in the Netherlands.

Since transport of heat has limitations, geothermal heat can only be used where there is demand in the vicinity of the resource. There are several examples of the profitable use of surplus geothermal heat enhancing local economic development. In Croatia, the development of a CHP plant using the geothermal resources of the Pannonian Basin has been welcomed by the community, since it enables additional developments aimed at stimulating the local economy. A new business and tourist facility is planned, with outdoor and indoor pools, greenhouses and fish farms. The project is expected to employ 265 people, 15 of them at the power plant.

Geothermal district cooling is poorly developed but could provide a summer use for geothermal district heating systems. Geothermal heat above 70°C can produce chilled water in sorption chillers that can be piped to consumers via the same circuit used for heating. Alternative devices such as fan coils and ceiling coolers can also be used. Sorption chillers have recently become available that can be driven by temperatures as low as 60oC, enabling geothermal heat drive compression chilling machines in place of electricity.

Enablers for development and use of geothermal energy

Whether a geothermal resource is used to produce electricity and/or heat, several disciplines and techniques will always be needed, notably resource assessment and means of accessing and engineering the resource.

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Resource assessment

Geothermal resources are found deep beneath the surface so exploration is needed to locate and assess them. Exploration consists of estimating underground temperature, permeability and the presence of fluid, as well as the lateral extent, depth and thickness of the resource, by using geosciences methods and by drilling exploration wells. The local state of stress must be assessed, too, particularly in the case of EGS. Exploration drilling involves high financial risks as it is expensive and the results are mainly unknown in advance. Wells in sedimentary, hydrothermal reservoirs, where geological formations resemble those exploited for oil and gas, can be drilled using similar methods. In contrast, economic drilling of low-cost exploration-only boreholes and drilling into deep, hard rock formations pose technical challenges requiring new and innovative solutions. Improvement of geophysical data inventories and geoscience exploration methods, as well as innovative geothermal resource assessment tools, will reduce the exploration risk and thus lower a barrier for investment in geothermal energy.

Accessing and engineering the resource

As well as aiding resource assessment, competitive drilling technology will make it easier to access and engineer geothermal resources. Reservoir stimulation technology is also extremely important, both for hydrothermal reservoirs, where the connection of a production well to the reservoir fluids requires improvement, and for creating EGS reservoirs in hot rock resources. Stimulation techniques to boost the conductivity and connectivity of hot rock resources will make it possible to access larger volumes of rock. Stimulation can be hydraulic, by injecting fluids, or chemical, by injecting acids or other substances that will dissolve the rock or the material filling the fractures. Both hydraulic fracturing and chemical stimulation techniques are similarly deployed in unconventional oil and gas reservoir developments. Hydraulic stimulation creates permeability, releasing seismic energy. In hydraulic fracturing, as in any sort of fluid injection or re-injection that raises underground fluid pressure, there is a risk of inducing micro-seismic events intense enough to be felt on the surface. Induced seismicity effects also depend on the existing stress field.

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Economics today

Where high-temperature hydrothermal resources are available, in many cases geothermal electricity is competitive with newly built conventional power plants. Binary plants can also achieve reasonable and competitive costs in several cases, but costs vary considerably depending on the size of the plant, the temperature level of the resource and the geographic location. EGS costs cannot yet be assessed accurately because the limited experience available has only been derived from pilot plants where economics are relatively unimportant. Geothermal heat may be competitive for district heating where a resource with sufficiently high temperatures is available and an adaptable district heating system is in place. Geothermal heat may also be competitive in applications where there is a high, continuous, heat demand and where there is no need for a large distribution system, e.g. in greenhouses. Although geothermal electricity and heat can be competitive under certain conditions, it will be necessary to reduce the levelised cost of energy (LCOE) of less conventional geothermal technology.

Investment costs

Geothermal electricity development costs vary considerably as they depend on a wide range of conditions, including resource temperature and pressure, reservoir depth and permeability, fluid chemistry, location, drilling market, size of development, number and type of plants (dry steam, flash, binary or hybrid), and whether the project is a greenfield site or expansion of an existing plant. Development costs are also strongly affected by the prices of commodities such as oil, steel and cement. In 2008, the capital costs of a greenfield geothermal electricity development ranged from USD 2 000/kWe to USD 4 000/kWe for flash plant developments and USD 2 400/kWe to USD 5 900/kWe for binary developments (IEA, 2010a). The highest investment costs for binary plants can be found in Europe in small binary developments (of a few MWe) used in conjunction with low- to medium-temperature resources. It is not yet possible to assess reliable investment data for EGS because it is still at the experimental stage.

Investments costs for district heating range from USD 570/kWt to USD 1 570/kWt (IPCC, forthcoming). For use of geothermal heat in greenhouses, investment costs range from USD 500/kWt to USD 1 000/kWt (ibid.).

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Operation and maintenance costs

Operation and maintenance (O&M) costs in geothermal electricity plants are limited, as geothermal plants require no fuel. Typical O&M costs depend on location and size of the facility, type and number of plants, and use of remote control; they range from USD 9/MWhe (large flash, binary in New Zealand) to USD 25/MWhe (small binary in USA), excluding well replacement drilling costs (IEA, 2010). When make-up wells are considered to be part of O&M costs, which is usual in the geothermal electric industry, O&M costs are estimated at USD 19/MWhe to USD 24 /MWhe as a worldwide average (IPCC, forthcoming), although they can be as low as USD 10/MWhe to USD 14 /MWhe in New Zealand (Barnett and Quinlivan, 2009).

Production costs

Levelised generation costs of geothermal power plants vary widely. On average, production costs for hydrothermal high temperature flash plants have been calculated to range from USD 50/MWhe to USD 80/MWhe. Production costs of hydrothermal binary plants vary on average from USD 60/MWhe to USD 110/MWhe (assumptions behind cost calculations are included in Appendix I). A recent case of a 30 MW binary development (United States) showed estimated levelised generation costs of USD 72/MWhe with a 15-year debt and 6.5% interest rate (IEA, 2010). New plant generation costs in some countries (e.g. New Zealand) are highly competitive (even without subsidies) at USD 50/MWhe to USD 70/ MWhe for known high-temperature resources. Some binary plants have higher upper limits: levelised costs for new greenfield plants can be as high as USD 120/MWhe in the United States and USD 200/MWhe in Europe, for small plants and lower-temperature resources. Estimated EGS development production costs range from USD 100/MWhe (for a 300°C resource at 4 km depth) to USD 190/MWhe (150°C resource at 5 km) in the United States, while European estimates are USD 250/MWhe to USD 300/MWhe (IEA, 2010a).

Use of geothermal energy for district space heating can have a wide range of costs depending on the specific use, the temperature of the resource and O&M and labour costs. District space heating costs range from USD 45/MWht to USD 85/MWht. Costs of heating greenhouses vary between USD 40/ MWht and USD 50/MWht (assumptions behind cost calculations are included in Appendix I).

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Conclusions and role of stakeholders

This roadmap has responded to requests from the G8 and other government leaders for more detailed analysis of the growth pathway for geothermal energy, a key energy source, within a portfolio of low-carbon energy technologies. It describes approaches and specific tasks regarding RDD&D; financing mechanisms; legal and regulatory frameworks; public engagement; and international collaboration. It provides regional projections for geothermal deployment from 2010 to 2050. Finally, this roadmap details actions and milestones to aid policy makers, industry, research institutes, as well as financial institutions, to implement geothermal energy (see also Table 1).

The geothermal roadmap is meant to be a process that evolves to take into account new technical and scientific developments, policies and international collaborative efforts. The roadmap has been designed with milestones that the international community can use to ensure that development efforts are on track to achieve the reductions in greenhouse-gas emissions that are required by 2050.

Below is a summary of actions needed by geothermal stakeholders, presented to indicate who should take the lead in specific efforts. In most cases, a broad range of actors will need to participate in each action. The IEA, together with government, industry and NGO stakeholders, will report regularly on the progress achieved toward this roadmap’s vision.